netdev - [PATCH net 03/11] ehea: remove ndo_poll

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Date:   Thu, 27 Sep 2018 09:31:53 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Michael Chan <michael.chan@...adcom.com>,
        Aviad Krawczyk <aviad.krawczyk@...wei.com>,
        Song Liu <songliubraving@...com>,
        Douglas Miller <dougmill@...ux.vnet.ibm.com>,
        Yisen Zhuang <yisen.zhuang@...wei.com>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Harish Patil <harish.patil@...ium.com>,
        Manish Chopra <manish.chopra@...ium.com>,
        Netanel Belgazal <netanel@...zon.com>,
        Solarflare linux maintainers <linux-net-drivers@...arflare.com>,
        Thomas Falcon <tlfalcon@...ux.vnet.ibm.com>
Subject: [PATCH net 03/11] ehea: remove ndo_poll_controller

As diagnosed by Song Liu, ndo_poll_controller() can
be very dangerous on loaded hosts, since the cpu
calling ndo_poll_controller() might steal all NAPI
contexts (for all RX/TX queues of the NIC). This capture
can last for unlimited amount of time, since one
cpu is generally not able to drain all the queues under load.

ehea uses NAPI for TX completions, so we better let core
networking stack call the napi->poll() to avoid the capture.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Douglas Miller <dougmill@...ux.vnet.ibm.com>
---
 drivers/net/ethernet/ibm/ehea/ehea_main.c | 14 --------------
 1 file changed, 14 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ehea/ehea_main.c b/drivers/net/ethernet/ibm/ehea/ehea_main.c
index ba580bfae512326d346e96e67718bec10ed716cc..03f64f40b2a3e0a3d9f3432cb6fbdd7bcd264a4c 100644
--- a/drivers/net/ethernet/ibm/ehea/ehea_main.c
+++ b/drivers/net/ethernet/ibm/ehea/ehea_main.c
@@ -921,17 +921,6 @@ static int ehea_poll(struct napi_struct *napi, int budget)
 	return rx;
 }
 
-#ifdef CONFIG_NET_POLL_CONTROLLER
-static void ehea_netpoll(struct net_device *dev)
-{
-	struct ehea_port *port = netdev_priv(dev);
-	int i;
-
-	for (i = 0; i < port->num_def_qps; i++)
-		napi_schedule(&port->port_res[i].napi);
-}
-#endif
-
 static irqreturn_t ehea_recv_irq_handler(int irq, void *param)
 {
 	struct ehea_port_res *pr = param;
@@ -2953,9 +2942,6 @@ static const struct net_device_ops ehea_netdev_ops = {
 	.ndo_open		= ehea_open,
 	.ndo_stop		= ehea_stop,
 	.ndo_start_xmit		= ehea_start_xmit,
-#ifdef CONFIG_NET_POLL_CONTROLLER
-	.ndo_poll_controller	= ehea_netpoll,
-#endif
 	.ndo_get_stats64	= ehea_get_stats64,
 	.ndo_set_mac_address	= ehea_set_mac_addr,
 	.ndo_validate_addr	= eth_validate_addr,
-- 
2.19.0.605.g01d371f741-goog